Effect of isobutyl-triethoxy-silane penetrative protective agent on the carbonation resistance of concrete

Effect of isobutyl-triethoxy-silane penetrative protective agent on the carbonation resistance of the concrete was studied. The concrete specimens for the 28 d accelerated carbonation process were manufactured with w/c of 0.49 and 0.64, both in the presence and absence of silane and mineral admixture. The penetration of isobutyl-triethoxy-silane and the carbonation of concrete were investigated by penetration depth, carbonation depth, XRD, SEM, and pore size distribution. The results showed that concrete compactness played an important role in the silane penetration and carbonation resistance. Penetration depth of silane-treated concrete mainly depended on the compactness of the concrete, and could not remarkably change through the accelerated carbonation process. In the accelerated carbonation process, penetrative protective agent improved the carbonation resistance of the higher compactness concretes but accelerated the carbonization process of the lower compactness concretes. As penetrative protective agent penetrated along the external connectivity pores into concrete not filling the entire surface area, the inorganic film could not fully protect the Ca(OH)2 phase from carbonation. After 28 d accelerated carbonation, fibrous hydration products disappeared and the surface holes decreased. Due to the formation of carbonized products, the porosity of the concrete surface decreased, especially in high-strength concrete.